Polytetrafluoroethylene has characteristics of excellent chemical durability as well as good smoothness, and thus is used as, for example, an additive to be added to grease requiring lubrication.
Patent Literature 1 discloses a powder of low-molecular-weight polytetrafluoroethylene containing a tetrafluoroethylene unit alone or a tetrafluoroethylene unit and a modifying monomer unit copolymerizable with the tetrafluoroethylene unit, wherein the low-molecular-weight polytetrafluoroethylene has an average primary particle size of 100 nm or smaller.
Since this powder has a small average primary particle size, it is dispersed with a small dispersed particle size when used as an additive for matrix material. Such a powder absorbs a large amount of oil, providing stable fine dispersion. Thus, the powder has a good effect of modifying the surface of the matrix material (for example, improving the texture of the coating surface), leading to reduction in the amount of the powder itself to be added.